This project is concerned with determining if optic nerve activity can be recorded from surface electrodes in human subjects, with a view toward developing a means of assessing the integrity of the visual pathways in clinical populations. We have performed spectral analysis on ERG waveforms recorded from the conjunctiva and temple of humans and cats and noted differences in the peaks of the power spectrum. We are presently evaluating the possibility that some of these spectral peaks are associated with optic nerve discharge. Such differences in spectra could derive from other than optic nerve discharge, and this has led us to investigate temporal muscle activity and the effects of different placement of electrodes as alternative explanations. We have also considered the possibility that pattern-elicited ERGs disappear after degeneration of the optic nerve fibers. After testing this idea in a monocularly deprived cat, we are currently recording steady-state ERGs in patients with optic neuritis. For the future, we intend to collect data on pattern-elicited ERGs and the spectral components observed at different spatial and temporal modulation in patients as well as continuing the correlative studies of conjunctival and optic nerve recordings in cats. We hope to determine if the magnitude and phase spectrum of flash-elicited ERGs differs systematically from those obtained with pattern stimulation in normal subjects and in patients with known optic disorders.